There are times we make promises and fully intend on keeping them. Our motives are pure and forsee no issue following through. But by some uncontrollable circumstance, we have to break that promise.
It's hard, there's disappointment, but we move on and try not to do it again. Other times however, we proclaim a promise with little to no intention of keeping it. Whether by lying to ourselves or lack of care for another person, we claim we'll do something only to purposely drop the ball later on.
The latter kind of promise is much more heinous. It's the equivalent of stringing someone along, leading them on. It's dirty, dishonest, and will tarnish your reputation in the long run. You may get away with it for a time, but those people you have stepped on to reach success will have no problem revealing your debt of promises to others.